During the startup process of conventional synchronous motors, the electro-magnet of the stator creates an alternating magnetic field which pulls the permanent magnetic rotor to oscillate. As the rotor obtains more kinetic energy, the oscillation magnitude of the rotor increases, and the rotor is eventually accelerated to be in synchronization with the alternating magnetic field of the stator. To ensure the successful startup, the motor is usually configured to have a low starting point, which makes the motor unable to operate at high efficiency operation point and hence leads to a low efficiency.